1. Field of the Invention
The present invention relates to an engine automatic-stop/restart system that automatically stops an engine when an automatic stopping condition is satisfied and then restarts the engine when a restarting condition is satisfied.
2. Description of the Related Art
In recent years, for the purpose of improving the gasoline mileage of a motor vehicle or the like and reducing an environmental load, there has been developed an engine automatic-stop/restart system that automatically cut off the supply of fuel so as to automatically stop an engine, when the operation of a driver, e.g., brake-pedal stepping-on operation while the motor vehicle travels at a speed lower than a predetermined speed, satisfies a predetermined condition for stopping the engine, and then restarts fuel injection so as to automatically restart the engine, when the operation of the driver satisfies a predetermined condition for restarting the engine, e.g., brake-pedal releasing operation, accelerator stepping-on operation, or the like.
To date, as such an engine automatic-stop/restart system, there has been proposed a system (for example, refer to Patent Document 1) in which when an engine restart request occurs after idling-stop driving is performed, speed-governing energization of the starter motor is started; at a time instant when the rotation speed of the starter motor becomes close to an anticipated rotation speed of the engine, the coupling between the pinion gear and the ring gear is started; at a time instant when the rotation speed of the motor (here means the rotation speed of the pinion gear, and the same applies hereinafter) and the rotation speed of the engine synchronize with each other, the coupling between the pinion gear and the ring gear is ended; after the end of the coupling, full-power energization of the starter motor is performed so that the starter motor drives the engine; then, the restart of the engine is completed.
In the case of the conventional system disclosed in Patent Document 1, before the rotation of the engine completely stops, the engagement between the pinion gear and the ring gear is realized; therefore, it is made possible to restart the engine rapidly.
To date, as such an engine automatic-stop/restart system, there has been proposed a system (for example, refer to Patent Document 2) in which the rotation speed of the engine is maintained by coupling the crankshaft of the engine and the wheel axle by the intermediary of a lockup clutch, and in the case where the rotation speed at a time when the restart request occurs is the same as or lower than a predetermined rotation speed, the starter motor is energized and then the starter motor drives the engine so as to complete the restart of the engine.
In the case of the conventional system disclosed in Patent Document 2, because the rotation speed of the engine is maintained by coupling the crankshaft of the engine and the wheel axle by the intermediary of a lockup clutch, it is made possible to restart the engine rapidly even in the case where the engine cannot be restarted by simply injecting a fuel.